For the manufacture of monocrystals of various metals, ceramics and the like, a number of techniques are known in the art as listed below.
(1) Unidirectional solidification involving melting followed by unidirectional cooling for solidification, resulting in aligned crystallographic orientation.
(2) Bridgman method involving pulling up a melt while allowing solidification in alignment with a monocrystalline plane.
(3) Zone melt method which is one form of the unidirectional solidification.
(4) Molding in a magnetic field.
(5) Vapor phase method including evaporation, sputtering, CVD, etc.
(6) Solid phase reaction method in which a ceramic monocrystal is prepared by interposing a flux of a material other than the elements of a ceramic such as glass between a monocrystal and a polycrystal and successively moving a heating zone, thereby utilizing movement of the flux along the grain boundary.
There are also known magnetostrictive materials in the form of RT.sub.2 intermetallic compounds such as RFe.sub.2. These materials are prepared (a) by unidirectional solidification and zone melting methods as disclosed in U.S. Pat. Nos. 4,308,474, 3,949,351, 4,378,258, 4,375,372, and 4,158,368.
Although it is described in these patents that monocrystals of RFe.sub.2 were obtained, Sm systems or the like could not be obtained in monocrystalline form because of peritectic formation during solidification. According to the report of the same inventor in IEEE Transactions on Magnetics, Vol. MAG.-22, No. 5, September 1986, (Tb.sub.x Dy.sub.1-x)Fe.sub.2 acquired (112) orientation. The (112) orientation, however, is low in magnetostriction, especially in magnetostriction during magnetization process as compared with (111) orientation.
Also, U.S. Pat. No. 4,308,474 discloses (b) RT.sub.2 prepared by Bridgman method. This does not yield a monocrystal oriented in (111) direction.
Further, U.S. Pat. No. 4,152,178 discloses (c) that molding is finished in a magnetic field in preparing RT.sub.2 by powder metallurgy. This does not yield a monocrystal.
No examples are known as to the use of solid phase reaction process for RT.sub.2 intermetallic compounds. This is also true for other R-T intermetallic compounds.